It has long been known to regulate sowing depth of a seed drill. The machine type referred to here is a seed drill of the type that is shown in the Swedish patent SE 527 842 and that has at least one sowing edge implement, such as a seed coulter, which suitably has at least one rotating disc, and which has a support, which regulates sowing depth. This support is suitably comprised of a rotating wheel but can also consist of for example a collector shoe. A common coulter type called V-disc comprises two discs placed at angles and between which is mounted a seed tube, which via flexible hoses, distributor and dosing device is connected to a hopper for seed and/or fertiliser. The seed coulter is commonly suspended with spring in the seed drill by means of an arm. Seed drills with this seed coulter construction can have individual depth setting often through the support wheel having an adjustment potential, which is advantageous for different crops, which require different sowing depths. Alternatively, all seed counters are depth-adjusted centrally or per section since a machine often has several sections. It must also be possible to lift the seed coulters out of the soil with sufficient clearance for transport driving on field or on road.
An implement of the above-mentioned type can be a seed coulter, which is adjustable in depth direction in relation to its support wheel (sowing depth setting). It has a variable downward force in order to be set for different soil types. The seed coulter ensures continuous contact against an uneven surface and also adjusts itself in a quick and stable way to the correct relative depth position when the machine is driven with good speed over an uneven field. It tolerates solid obstructions such as stones and it is adapted so that it can be lifted up out of the soil to a sufficient clearance height that can be up to approx. 300 mm.
Known technology often utilises an adjustment where the depth of each seed coulter is adjusted manually. On larger seed drills with perhaps 60-100 seed coulters this is obviously very impractical.
Depth setting can also occur centrally. It usually occurs through two systems, one where an implement bearing beam is brought into a predetermined height position through the entire machine being adjusted to this height or another where the machines has joints and a separate hydraulic cycle for this purpose. Another hydraulic cycle exerts the spring power of the seed coulters towards the soil. Such exertion also occurs manually through crank handles on certain machine types. These known systems are complex and complicated in their construction and function.